OF NATURAL PHILOSOPHY. 345 



(382.) To botany many of the same remarks apply. 

 Its artificial systems of classification, however con- 

 venient, have not prevented botanists from endea- 

 vouring to group together the objects of their 

 science in natural classes having a community of 

 character more intimate than those which deter- 

 mine their place in the Linnean or any similar 

 system ; a community of character extending over 

 the whole habit and properties of the individuals 

 compared. The important chemical discoveries 

 which have been lately made of peculiar proximate 

 principles which, in an especial manner, characterize 

 certain families of plants, hold out the prospect of a 

 greatly increased field of interesting knowledge in 

 this direction, and not only interesting, but in a 

 high degree important, when it is considered that 

 the principles thus brought into view are, for the 

 most part, very powerful medicines, and are, in fact, 

 the essential ingredients on which the medical 

 virtues of the plants depend. The law of the dis- 

 tribution of the generic forms of plants over the 

 globe, too, has. within a comparatively recent period, 

 become an object of study to the naturalist ; and its 

 connection with the laws of climate constitutes one 

 of the most interesting and important branches of 

 natural-historical enquiry, and one on which great 

 light remains to be thrown by future researches. 

 It is this which constitutes the chief connecting 

 link between botany and geology, and renders a 

 knowledge of the vegetable fossils, of any portion of 

 the earth's surface, indispensable to the formation 

 of a correct judgment of the circumstances under 

 which it existed in its ancient state. Fossil botany 



